This week, the appearance of weapons at rallies near President Obama in Portsmouth , N.H., and Phoenix chilled many Americans, even as the White House and Secret Service played down the threat, saying current security procedures are sufficient to protect "Renegade," the Secret Service's nickname for the country's first black president.

But behind the scenes, security experts say, the Secret Service is likely concerned. In a country where extremist anger has moved into the mainstream on some fronts, Mr. Obama and his ear-pieced protectors have to carefully walk a line between taking new threats seriously while protecting people's rights, including the constitutional right to bear arms. Indeed, assassination fears have dogged Obama's candidacy and presidency, making him the most protected president in US history.

So far, the gun-wielding protesters have been too far removed from the president to pose any threat. But experts say this new phenomenon of guns at public events may require adjustments in how the president operates.

The threat, they say, is not necessarily the gun-carrying protesters themselves. Rather, their actions could embolden the nation's angriest fringe. The specter of so-called "lone wolf" acts of violence is already high on the nation's law enforcement agenda.

It's imperative for the White House not to underestimate the danger allowing firearms near the president, he says. "That's why I don't care what the political concerns are, but the people who are obligated to provide Obama protection are going to be right now changing things," Mr. Levin adds.

The White House isn't likely to signal any changes, but alterations could include widening the gun-free perimeter around the president, limiting his public exposure, and more carefully vetting venues, experts say.

Former Secret Service Agent Joseph Petro, the author of "Standing Next to History," says gun-wielding protesters do run the risk of distracting local police and the Secret Service from their job.

But he agrees with Levin that greatest concern is the message this sends to those who would wish to harm the president. "These people could be stimulating, encouraging, inciting the nut cases on the fringe that might actually want to do something either against the president or a group of people," Mr. Petro says. "It's creating a very negative and dangerous atmosphere at these protests. The real question is: What kind of country do we want to be? This is like the Wild West, and I thought we got over that."

"In some ways, [gun-control proponents] have lost, and ... the only people who really think [these incidents] are deviant are people whose whole world view is that ordinary, law-abiding citizens shouldn't have a reason to carry guns," he says.